Method for altering drug pharmacokinetics based on medical delivery platform

ABSTRACT

A method for directly delivering whereby a substance is introduced into an intradermal space within mammalian skin which involves administering the substance through at least one small gauge hollow needle having an outlet with an exposed height between 0 and 1 mm. The outlet is inserted into the skin to a depth of between 0.3 mm and 2 mm such that the delivery of the substance occurs at a depth between 0.3 mm and 2 mm.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 12/100,259,filed Apr. 9, 2008 now abandoned, which is a divisional of applicationSer. No. 09/893,746, filed Jun. 29, 2001 now abandoned, which is acontinuation-in-part of application Ser. No. 09/606,909, filed Jun. 29,2000 now U.S. Pat. No. 8,465,468, each of which is hereby incorporatedby reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to methods and devices for administrationof substances into the intradermal layer of skin.

BACKGROUND OF THE INVENTION

The importance of efficiently and safely administering pharmaceuticalsubstances such as diagnostic agents and drugs has long been recognized.Although an important consideration for all pharmaceutical substances,obtaining adequate bioavailability of large molecules such as proteinsthat have arisen out of the biotechnology industry has recentlyhighlighted this need to obtain efficient and reproducible absorption(Cleland et al., Curr. Opin. Biotechnol. 12: 212-219, 2001). The use ofconventional needles has long provided one approach for deliveringpharmaceutical substances to humans and animals by administrationthrough the skin. Considerable effort has been made to achievereproducible and efficacious delivery through the skin while improvingthe ease of injection and reducing patient apprehension and/or painassociated with conventional needles. Furthermore, certain deliverysystems eliminate needles entirely, and rely upon chemical mediators orexternal driving forces such as iontophoretic currents orelectroporation or thermal poration or sonophoresis to breach thestratum corneum, the outermost layer of the skin, and deliver substancesthrough the surface of the skin. However, such delivery systems do notreproducibly breach the skin barriers or deliver the pharmaceuticalsubstance to a given depth below the surface of the skin andconsequently, clinical results can be variable. Thus, mechanical breachof the stratum corneum such as with needles, is believed to provide themost reproducible method of administration of substances through thesurface of the skin, and to provide control and reliability in placementof administered substances.

Approaches for delivering substances beneath the surface of the skinhave almost exclusively involved transdermal administration, i.e.delivery of substances through the skin to a site beneath the skin.Transdermal delivery includes subcutaneous, intramuscular or intravenousroutes of administration of which, intramuscular (IM) and subcutaneous(SC) injections have been the most commonly used.

Anatomically, the outer surface of the body is made up of two majortissue layers, an outer epidermis and an underlying dermis, whichtogether constitute the skin (for review, see Physiology, Biochemistry,and Molecular Biology of the Skin, Second Edition, L. A. Goldsmith, Ed.,Oxford University Press, New York, 1991). The epidermis is subdividedinto five layers or strata of a total thickness of between 75 and 150μm. Beneath the epidermis lies the dermis, which contains two layers, anoutermost portion referred to at the papillary dermis and a deeper layerreferred to as the reticular dermis. The papillary dermis contains vastmicrocirculatory blood and lymphatic plexuses. In contrast, thereticular dermis is relatively acellular and avascular and made up ofdense collagenous and elastic connective tissue. Beneath the epidermisand dermis is the subcutaneous tissue, also referred to as thehypodermis, which is composed of connective tissue and fatty tissue.Muscle tissue lies beneath the subcutaneous tissue.

As noted above, both the subcutaneous tissue and muscle tissue have beencommonly used as sites for administration of pharmaceutical substances.The dermis, however, has rarely been targeted as a site foradministration of substances, and this may be due, at least in part, tothe difficulty of precise needle placement into the intradermal space.Furthermore, even though the dermis, in particular, the papillary dermishas been known to have a high degree of vascularity, it has notheretofore been appreciated that one could take advantage of this highdegree of vascularity to obtain an improved absorption profile foradministered substances compared to subcutaneous administration. This isbecause small drug molecules are typically rapidly absorbed afteradministration into the subcutaneous tissue which has been far moreeasily and predictably targeted than the dermis has been. On the otherhand, large molecules such as proteins are typically not well absorbedthrough the capillary epithelium regardless of the degree of vascularityso that one would not have expected to achieve a significant absorptionadvantage over subcutaneous administration by the more difficult toachieve intradermal administration even for large molecules.

One approach to administration beneath the surface to the skin and intothe region of the intradermal space has been routinely used in theMantoux tuberculin test. In this procedure, a purified proteinderivative is injected at a shallow angle to the skin surface using a 27or 30 gauge needle (Flynn et al, Chest 106: 1463-5, 1994). A degree ofuncertainty in placement of the injection can, however, result in somefalse negative test results. Moreover, the test has involved a localizedinjection to elicit a response at the site of injection and the Mantouxapproach has not led to the use of intradermal injection for systemicadministration of substances.

Some groups have reported on systemic administration by what has beencharacterized as “intradermal” injection. In one such report, acomparison study of subcutaneous and what was described as “intradermal”injection was performed (Autret et al, Therapie 46:5-8, 1991). Thepharmaceutical substance tested was calcitonin, a protein of a molecularweight of about 3600. Although it was stated that the drug was injectedintradermally, the injections used a 4 mm needle pushed up to the baseat an angle of 60. This would have resulted in placement of theinjectate at a depth of about 3.5 mm and into the lower portion of thereticular dermis or into the subcutaneous tissue rather than into thevascularized papillary dermis. If, in fact, this group injected into thelower portion of the reticular dermis rather than into the subcutaneoustissue, it would be expected that the substance would either be slowlyabsorbed in the relatively less vascular reticular dermis or diffuseinto the subcutaneous region to result in what would be functionally thesame as subcutaneous administration and absorption. Such actual orfunctional subcutaneous administration would explain the reported lackof difference between subcutaneous and what was characterized asintradermal administration, in the times at which maximum plasmaconcentration was reached, the concentrations at each assay time and theareas under the curves.

Similarly, Bressolle et al. administered sodium ceftazidime in what wascharacterized as “intradermal” injection using a 4 mm needle (Bressolleet al. J. Pharm. Sci. 82:1175-1178, 1993). This would have resulted ininjection to a depth of 4 mm below the skin surface to produce actual orfunctional subcutaneous injection, although good subcutaneous absorptionwould have been anticipated in this instance because sodium ceftazidimeis hydrophilic and of relatively low molecular weight.

Another group reported on what was described as an intradermal drugdelivery device (U.S. Pat. No. 5,007,501). Injection was indicated to beat a slow rate and the injection site was intended to be in some regionbelow the epidermis, i.e., the interface between the epidermis and thedermis or the interior of the dermis or subcutaneous tissue. Thisreference, however, provided no teachings that would suggest a selectiveadministration into the dermis nor did the reference suggest anypossible pharmacokinetic advantage that might result from such selectiveadministration.

Thus there remains a continuing need for efficient and safe methods anddevices for administration of pharmaceutical substances.

SUMMARY OF THE INVENTION

The present disclosure relates to a new parenteral administration methodbased on directly targeting the dermal space whereby such methoddramatically alters the pharmacokinetics (PK) and pharmacodynamics (PD)parameters of administered substances. By the use of direct intradermal(ID) administration means hereafter referred to as dermal-access means,for example, using microneedle-based injection and infusion systems (orother means to accurately target the intradermal space), thepharmacokinetics of many substances including drugs and diagnosticsubstances, which are especially protein and peptide hormones, can bealtered when compared to traditional parental administration routes ofsubcutaneous and intravenous delivery. These findings are pertinent notonly to microdevice-based injection means, but other delivery methodssuch as needless or needle-free ballistic injection of fluids or powdersinto the ID space, Mantoux-type ID injection, enhanced iontophoresisthrough microdevices, and direct deposition of fluid, solids, or otherdosing forms into the skin. Disclosed is a method to increase the rateof uptake for parenterally-administered drugs without necessitating IVaccess. One significant beneficial effect of this delivery method isproviding a shorter T_(max).(time to achieve maximum blood concentrationof the drug). Potential corollary benefits include higher maximumconcentrations for a given unit dose (C_(max)), higher bioavailability,more rapid uptake rates, more rapid onset of pharmacodynamics orbiological effects, and reduced drug depot effects. According to thepresent invention, improved pharmacokinetics means increasedbioavailability, decreased lag time (T_(lag)), decreased T_(max), morerapid absorption rates, more rapid onset and/or increased C_(max) for agiven amount of compound administered, compared to subcutaneous,intramuscular or other non-IV parenteral means of drug delivery.

By bioavailability is meant the total amount of a given dosage thatreached the blood compartment. This is generally measured as the areaunder the curve in a plot of concentration vs. time. By “lag time” ismeant the delay between the administration of a compound and time tomeasurable or detectable blood or plasma levels. T_(max) is a valuerepresenting the time to achieve maximal blood concentration of thecompound, and C_(max) is the maximum blood concentration reached with agiven dose and administration method. The time for onset is a functionof T_(lag), T_(max) and C_(max), as all of these parameters influencethe time necessary to achieve a blood (or target tissue) concentrationnecessary to realize a biological effect. T_(max) and C_(max) can bedetermined by visual inspection of graphical results and can oftenprovide sufficient information to compare two methods of administrationof a compound. However, numerical values can be determined moreprecisely by analysis using kinetic models (as described below) and/orother means known to those of skill in the art.

Directly targeting the dermal space as taught by the invention providesmore rapid onset of effects of drugs and diagnostic substances. Theinventors have found that substances can be rapidly absorbed andsystemically distributed via controlled ID administration thatselectively accesses the dermal vascular and lymphatic microcapillaries,thus the substances may exert their beneficial effects more rapidly thanSC administration. This has special significance for drugs requiringrapid onset, such as insulin to decrease blood glucose, pain relief suchas for breakthrough cancer pain, or migraine relief, or emergency rescuedrugs such as adrenaline or anti-venom. Natural hormones are alsoreleased in pulsatile fashion with a rapid onset burst followed by rapidclearance. Examples include insulin that is released in response tobiological stimulus, for example high glucose levels. Another example isfemale reproductive hormones, which are released at time intervals inpulsatile fashion. Human growth hormone is also released in normalpatients in a pulsatile fashion during sleep. This benefit allows bettertherapy by mimicking the natural body rhythms with synthetic drugcompounds. Likewise, it may better facilitate some current therapiessuch as blood glucose control via insulin delivery. Many currentattempts at preparing “closed loop” insulin pumps are hindered by thedelay period between administering the insulin and waiting for thebiological effect to occur. This makes it difficult to ascertain inreal-time whether sufficient insulin has been given, withoutovertitrating and risking hypoglycemia. The more rapid PK/PD of IDdelivery eliminates much of this type of problem.

Mammalian skin contains two layers, as discussed above, specifically,the epidermis and dermis. The epidermis is made up of five layers, thestratum corneum, the stratum lucidum, the stratum granulosum, thestratum spinosum and the stratum germinativum and the dermis is made upof two layers, the upper papillary dermis and the deeper reticulardermis. The thickness of the dermis and epidermis varies from individualto individual, and within an individual, at different locations on thebody. For example, it has been reported that the epidermis varies inthickness from about 40 to about 90 μm and the dermis varies inthickness ranging from just below the epidermis to a depth of from lessthan 1 mm in some regions of the body to just under 2 to about 4 mm inother regions of the body depending upon the particular study report(Hwang et al., Ann Plastic Surg 46:327-331, 2001; Southwood, Plast.Reconstr. Surg 15:423-429, 1955; Rushmer et al., Science 154:343-348,1966).

As used herein, intradermal is intended to mean administration of asubstance into the dermis in such a manner that the substance readilyreaches the richly vascularized papillary dermis and is rapidly absorbedinto the blood capillaries and/or lymphatic vessels to becomesystemically bioavailable. Such can result from placement of thesubstance in the upper region of the dermis, i.e. the papillary dermisor in the upper portion of the relatively less vascular reticular dermissuch that the substance readily diffuses into the papillary dermis. Itis believed that placement of a substance predominately at a depth of atleast about 0.3 mm, more preferably, at least about 0.4 mm and mostpreferably at least about 0.5 mm up to a depth of no more than about 2.5mm, more preferably, no more than about 2.0 mm and most preferably nomore than about 1.7 mm will result in rapid absorption of macromolecularand/or hydrophobic substances. Placement of the substance predominatelyat greater depths and/or into the lower portion of the reticular dermisis believed to result in the substance being slowly absorbed in the lessvascular reticular dermis or in the subcutaneous region either of whichwould result in reduced absorption of macromolecular and/or hydrophobicsubstances. The controlled delivery of a substance in this dermal spacebelow the papillary dermis in the reticular dermis, but sufficientlyabove the interface between the dermis and the subcutaneous tissue,should enable an efficient (outward) migration of the substance to the(undisturbed) vascular and lymphatic microcapillary bed (in thepapillary dermis), where it can be absorbed into systemic circulationvia these microcapillaries without being sequestered in transit by anyother cutaneous tissue compartment.

Another benefit of the invention is to achieve more rapid systemicdistribution and offset of drugs or diagnostic agents. This is alsopertinent for many hormones that in the body are secreted in a pulsatilefashion. Many side effects are associated with having continuouscirculating levels of substances administered. A very pertinent exampleis female reproductive hormones that actually have the opposite effect(cause infertility) when continuously present in the blood. Likewise,continuous and elevated levels of insulin are suspected to down regulateinsulin receptors both in quantity and sensitivity.

Another benefit of the invention is to achieve higher bioavailabilitiesof drugs or diagnostic agents. This effect has been most dramatic for IDadministration of high molecular weight substances, especially proteins,peptides, and polysaccharides. The direct benefit is that IDadministration with enhanced bioavailability, allows equivalentbiological effects while using less active agent. This results in directeconomic benefit to the drug manufacturer and perhaps consumer,especially for expensive protein therapeutics and diagnostics. Likewise,higher bioavailability may allow reduced overall dosing and decrease thepatient's side effects associated with higher dosing.

Another benefit of the invention is the attainment of higher maximumconcentrations of drugs or diagnostic substances. The inventors havefound that substances administered ID are absorbed more rapidly, withbolus administration resulting in higher initial concentrations. This ismost beneficial for substances whose efficacy is related to maximalconcentration. The more rapid onset allows higher C_(Max) values to bereached with lesser amounts of the substance. Therefore, the dose can bereduced, providing an economic benefit, as well as a physiologicalbenefit since lesser amounts of the drug or diagnostic agent has to becleared by the body.

Another benefit of the invention is no change in systemic eliminationrates or intrinsic clearance mechanisms of drugs or diagnostic agents.All studies to date by the applicants have maintained the same systemicelimination rate for the substances tested as via IV or SC dosingroutes. This indicates this dosing route has no change in the biologicalmechanism for systemic clearance. This is an advantageous from aregulatory standpoint, since degradation and clearance pathways need notbe reinvestigated prior to filing for FDA approval. This is alsobeneficial from a pharmacokinetics standpoint, since it allowspredictability of dosing regimes. Some substances may be eliminated fromthe body more rapidly if their clearance mechanism are concentrationdependent. Since ID delivery results in higher Cmax, clearance rate maybe increased, although the intrinsic mechanism remains unchanged.

Another benefit of the invention is no change in pharmacodynamicmechanism or biological response mechanism. As stated above,administered drugs by the methods taught by the applicants still exerttheir effects by the same biological pathways that are intrinsic toother delivery means. Any pharmacodynamic changes are related only tothe difference patterns of appearance, disappearance, and drug ordiagnostic agent concentrations present in the biological system.

Using the methods of the present invention, pharmaceutical compounds maybe administered as a bolus, or by infusion. As used herein, the term“bolus” is intended to mean an amount that is delivered within a timeperiod of less than ten (10) minutes. “Infusion” is intended to mean thedelivery of a substance over a time period greater than ten (10) minutesIt is understood that bolus administration or delivery can be carriedout with rate controlling means, for example a pump, or have no specificrate controlling means, for example user self-injection.

Another benefit of the invention is removal of the physical or kineticbarriers invoked when drugs passes through and becomes trapped incutaneous tissue compartments prior to systemic absorption. Eliminationof such barriers leads to an extremely broad applicability to variousdrug classes. Many drugs administered subcutaneously exert this depoteffect—that is, the drug is slowly released from the SC space, in whichit is trapped, as the rate determining step prior to systemicabsorption, due to affinity for or slow diffusion through the fattyadipose tissue. This depot effect results in a lower C_(max) and longerT_(max), compared to ID, and can result in high inter-individualvariability of absorption. This effect is also pertinent for comparisonto transdermal delivery methods including passive patch technology, withor without permeation enhances, iontophoretic technology, sonopheresis,or stratum corneum ablation or disruptive methods. Transdermal patchtechnology relies on drug partitioning through the highly impermeablestratum corneum and epidermal barriers. Few drugs except highlylipophilic compounds can breach this barrier, and those that do, oftenexhibit extended offset kinetics due to tissue saturation andentrappment of the drugs. Active transdermal means, while often fasterthan passive transfer means, are still restricted to compound classesthat can be moved by charge repulsion or other electronic orelectrostatic means, or carried passively through the transient porescaused by cavitation of the tissue during application of sound waves.The stratum corneum and epidermis still provide effective means forinhibiting this transport. Stratum corneum removal by thermal or laserablation, abrasive means or otherwise, still lacks a driving force tofacilitate penetration or uptake of drugs. Direct ID administration bymechanical means overcomes the kinetic barrier properties of skin, andis not limited by the pharmaceutical or physicochemical properties ofthe drug or its formulation excipients.

Another benefit of the invention is highly controllable dosing regimens.The applicants have determined that ID infusion studies havedemonstrated dosing profiles that are highly controllable andpredictable due to the rapid onset and offset kinetics of drugs ordiagnostic agents delivered by this route. This allows almost absolutecontrol over the desired dosing regimen when ID delivery is coupled witha fluid control means or other control system to regulate metering ofthe drug or diagnostic agent into the body. This single benefit alone isone of the principal goals of most drug or diagnostic agent deliverymethods. Bolus ID substance administration as defined previously resultsin kinetics most similar to IV injection and is most desirable for painrelieving compounds, mealtime insulin, rescue drugs, erectiledysfunction compounds, or other drugs that require rapid onset. Alsoincluded would be combinations of substances capable of acting alone orsynergistically. Extending the ID administration duration via infusioncan effectively mimic SC uptake parameters, but with betterpredictability. This profile is particularly good for substances such asgrowth hormones, or analgesics. Longer duration infusion, typically atlower infusion rates can result in continuous low basal levels of drugsthat is desired for anticoagulants, basal insulin, and chronic paintherapy. These kinetic profiles can be combined in multiple fashion toexhibit almost any kinetic profile desired. An example would be topulsatile delivery of fertility hormone (LHRH) for pregnancy induction,which requires intermittent peaks every 90 minutes with total clearancebetween pulses. Other examples would be rapid peak onset of drugs formigraine relief, followed by lower levels for pain prophylaxis.

Another benefit of the invention is reduced degradation of drugs anddiagnostic agents and/or undesirable immunogenic activity. Transdermalmethods using chemical enhancers or iontophoresis, or sonophoresis orelectroporation or thermal poration require that a drug pass through theviable epidermal layer, which has high metabolic and immunogenicactivity. Metabolic conversion of substances in the epidermis orsequestration by immunoglobulins reduces the amount of drug availablefor absorption. The ID administration circumvents this problem byplacing the drug directly in the dermis, thus bypassing the epidermisentirely.

These and other benefits of the invention are achieved by directlytargeting absorption by the papillary dermis and by controlled deliveryof drugs, diagnostic agents, and other substances to the dermal space ofskin. The inventors have found that by specifically targeting theintradermal space and controlling the rate and pattern of delivery, thepharmacokinetics exhibited by specific drugs can be unexpectedlyimproved, and can in many situations be varied with resulting clinicaladvantage. Such pharmacokenetics cannot be as readily obtained orcontrolled by other parenteral administration routes, except by IVaccess.

The present invention improves the clinical utility of ID delivery ofdrugs, diagnostic agents, and other substances to humans or animals. Themethods employ dermal-access means (for example a small gauge needle,especially microneedles), to directly target the intradermal space andto deliver substances to the intradermal space as a bolus or byinfusion. It has been discovered that the placement of the dermal-accessmeans within the dermis provides for efficacious delivery andpharmacokinetic control of active substances. The dermal-access means isso designed as to prevent leakage of the substance from the skin andimprove adsorption within the intradermal space. The pharmacokinetics ofhormone drugs delivered according to the methods of the invention havebeen found to be vastly different to the pharmacokinetics ofconventional SC delivery of the drug, indicating that ID administrationaccording to the methods of the invention will provide improved clinicalresults. Delivery devices that place the dermal-access means at anappropriate depth in the intradermal space and control the volume andrate of fluid delivery provide accurate delivery of the substance to thedesired location without leakage.

Disclosed is a method to increase the rate of uptake forparenterally-administered drugs without necessitating IV access. Thiseffect provides a shorter T_(max). Potential corollary benefits includehigher maximum concentrations for a given unit dose (C_(max)), higherbioavailability, more rapid onset of pharmacodynamics or biologicaleffects, and reduced drug depot effects.

It has also been found that by appropriate depth control of thedermal-access means within the intradermal space that thepharmacokinetics of hormone drugs delivered according to the methods ofthe invention can, if required, produce similar clinical results to thatof conventional SC delivery of the drug.

The pharmacokinetic profile for individual compounds will vary accordingto the chemical properties of the compounds. For example, compounds thatare relatively large, having a molecular weight of at least 1000 Daltonsas well as larger compounds of at least 2000 Daltons, at least 4000Daltons, at least 10,000 Daltons and larger and/or hydrophobic compoundsare expected to show the most significant changes compared totraditional parenteral methods of administration, such as intramuscular,subcutaneous or subdermal injection. It is expected that smallhydrophilic substances, on the whole, will exhibit similar kinetics forID delivery compared to other methods.

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a time course of plasma insulin levels of intradermalversus subcutaneous bolus administration of fast-acting.

FIG. 2 shows a time course of blood glucose levels of intradermal versussubcutaneous bolus administration of fast-acting insulin.

FIG. 3 shows a comparison of bolus ID dosing of fast-acting versusregular insulin.

FIG. 4 shows the effects of different intradermal injection depths forbolus dosing of fast-acting insulin on the time course of insulin levels

FIG. 5 shows a comparison of the time course of insulin levels for bolusdosing of long-acting insulin administered subcutaneously orintradermally.

FIGS. 6 and 7 show a comparison of the pharmacokinetic availability andthe pharmacodynamic results of granulocyte colony stimulating factordelivered intradermally with a single needle or three point needlearray, subcutaneously, or intravenously.

FIGS. 8, 9 and 10 show a comparison of low molecular weight heparinintradermal delivery by bolus, short duration, long duration infusionwith comparison to subcutaneous infusion.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a method for therapeutic treatment bydelivery of a drug or other substance to a human or animal subject bydirectly targeting the intradermal space, where the drug or substance isadministered to the intradermal space through one or more dermal-accessmeans incorporated within the device. Substances infused according tothe methods of the invention have been found to exhibit pharmacokineticssuperior to, and more clinically desirable than that observed for thesame substance administered by SC injection.

The dermal-access means used for ID administration according to theinvention is not critical as long as it penetrates the skin of a subjectto the desired targeted depth within the intradermal space withoutpassing through it. In most cases, the device will penetrate the skinand to a depth of about 0.5-2 mm. The dermal-access means may compriseconventional injection needles, catheters or microneedles of all knowntypes, employed singularly or in multiple needle arrays. Thedermal-access means may comprise needleless devices including ballisticinjection devices. The terms “needle” and “needles” as used herein areintended to encompass all such needle-like structures The termmicroneedles as used herein are intended to encompass structures smallerthan about 30 gauge, typically about 31-50 gauge when such structuresare cylindrical in nature. Non-cylindrical structures encompass by theterm microneedles would therefore be of comparable diameter and includepyramidal, rectangular, octagonal, wedged, and other geometrical shapes.Dermal-access means also include ballistic fluid injection devices,powder-jet delivery devices, piezoelectric, electromotive,electromagnetic assisted delivery devices, gas-assisted deliverydevices, of which directly penetrate the skin to provide access fordelivery or directly deliver substances to the targeted location withinthe dermal space. By varying the targeted depth of delivery ofsubstances by the dermal-access means, pharmacokinetic andpharmacodynamic (PK/PD) behavior of the drug or substance can betailored to the desired clinical application most appropriate for aparticular patient's condition. The targeted depth of delivery ofsubstances by the dermal-access means may be controlled manually by thepractitioner, or with or without the assistance of indicator means toindicate when the desired depth is reached. Preferably however, thedevice has structural means for controlling skin penetration to thedesired depth within the intradermal space. This is most typicallyaccomplished by means of a widened area or hub associated with the shaftof the dermal-access means that may take the form of a backing structureor platform to which the needles are attached. The length ofmicroneedles as dermal-access means are easily varied during thefabrication process and are routinely produced in less than 2 mm length.Microneedles are also a very sharp and of a very small gauge, to furtherreduce pain and other sensation during the injection or infusion. Theymay be used in the invention as individual single-lumen microneedles ormultiple microneedles may be assembled or fabricated in linear arrays ortwo-dimensional arrays as to increase the rate of delivery or the amountof substance delivered in a given period of time. Microneedles may beincorporated into a variety of devices such as holders and housings thatmay also serve to limit the depth of penetration. The dermal-accessmeans of the invention may also incorporate reservoirs to contain thesubstance prior to delivery or pumps or other means for delivering thedrug or other substance under pressure. Alternatively, the devicehousing the dermal-access means may be linked externally to suchadditional components.

IV-like pharmacokinetics is accomplished by administering drugs into thedermal compartment in intimate contact with the capillarymicrovasculature and lymphatic microvasculature. In should be understoodthat the terms microcapillaries or capillary beds refer to eithervascular or lymphatic drainage pathways within the dermal area.

While not intending to be bound by any theoretical mechanism of action,it is believed that the rapid absorption observed upon administrationinto the dermis is achieved as a result of the rich plexuses of bloodand lymphatic vessels in the dermis. However, the presence of blood andlymphatic plexuses in the dermis would not by itself be expected toproduce an enhanced absorption of macromolecules. This is becausecapillary endothelium is normally of low permeability or impermeable tomacromolecules such as proteins, polysaccharides, nucleic acid polymers,substance having polymers attached such as pegylated proteins and thelike. Such macromolecules have a molecular weight of at least 1000Daltons or of a higher molecular weight of at least, 2000 Daltons, atleast 4000 Daltons, at least 10,000 Daltons or even higher. Furthermore,a relatively slow lymphatic drainage from the interstitium into thevascular compartment would also not be expected to produce a rapidincrease in plasma concentration upon placement of a pharmaceuticalsubstance into the dermis.

One possible explanation for the unexpected enhanced absorption reportedherein is that upon injection of substances so that they readily reachthe papillary dermis an increase in blood flow and capillarypermeability results. For example, it is known that a pinprick insertionto a depth of 3 mm produces an increase in blood flow and this has beenpostulated to be independent of pain stimulus and due to tissue releaseof histamine (Arildsson et al., Microvascular Res. 59:122-130, 2000).This is consistent with the observation that an acute inflammatoryresponse elicited in response to skin injury produces a transientincrease in blood flow and capillary permeability (see Physiology,Biochemistry, and Molecular Biology of the Skin, Second Edition, L. A.Goldsmith, Ed., Oxford Univ. Press, New York, 1991, p. 1060; Wilhem,Rev. Can. Biol. 30:153-172, 1971). At the same time, the injection intothe intradermal layer would be expected to increase interstitialpressure. It is known that increasing interstitial pressure from values(beyond the “normal range”) of about −7 to about +2 mmHg distendslymphatic vessels and increases lymph flow (Skobe et al., J. Investig.Dermatol. Symp. Proc. 5:14-19, 2000). Thus, the increased interstitialpressure elicited by injection into the intradermal layer is believed toelicit increased lymph flow and increased absorption of substancesinjected into the dermis.

By “improved pharmacokinetics” it is meant that an enhancement ofpharmacokinetic profile is achieved as measured, for example, bystandard pharmacokinetic parameters such as time to maximal plasmaconcentration (T_(max)), the magnitude of maximal plasma concentration(C_(max)) or the time to elicit a minimally detectable blood or plasmaconcentration (T_(lag)). By enhanced absorption profile, it is meantthat absorption is improved or greater as measured by suchpharmacokinetic parameters. The measurement of pharmacokineticparameters and determination of minimally effective concentrations areroutinely performed in the art. Values obtained are deemed to beenhanced by comparison with a standard route of administration such as,for example, subcutaneous administration or intramuscularadministration. In such comparisons, it is preferable, although notnecessarily essential, that administration into the intradermal layerand administration into the reference site such as subcutaneousadministration involve the same dose levels, i.e. the same amount andconcentration of drug as well as the same carrier vehicle and the samerate of administration in terms of amount and volume per unit time.Thus, for example, administration of a given pharmaceutical substanceinto the dermis at a concentration such as 100 μg/ml and rate of 100 μLper minute over a period of 5 minutes would, preferably, be compared toadministration of the same pharmaceutical substance into thesubcutaneous space at the same concentration of 100 μg/ml and rate of100 μL per minute over a period of 5 minutes.

The enhanced absorption profile is believed to be particularly evidentfor substances which are not well absorbed when injected subcutaneouslysuch as, for example, macromolecules and/or hydrophobic substances.Macromolecules are, in general, not well absorbed subcutaneously andthis may be due, not only to their size relative to the capillary poresize, it may also be due to their slow diffusion through theinterstitium because of their size. It is understood that macromoleculescan possess discrete domains having a hydrophobic and/or hydrophilicnature. In contrast, small molecules which are hydrophilic are generallywell absorbed when administered subcutaneously and it is possible thatno enhanced absorption profile would be seen upon injection into thedermis compared to absorption following subcutaneous administration.Reference to hydrophobic substances herein is intended to mean lowmolecular weight substances, for example substances with molecularweights less than 1000 Daltons, which have a water solubility which islow to substantially insoluble

The above-mentioned PK and PD benefits are best realized by accuratedirect targeting of the dermal capillary beds. This is accomplished, forexample, by using microneedle systems of less than about 250 micronouter diameter, and less than 2 mm exposed length. Such systems can beconstructed using known methods of various materials including steel,silicon, ceramic, and other metals, plastic, polymers, sugars,biological and or biodegradable materials, and/or combinations thereof.

It has been found that certain features of the intradermaladministration methods provide clinically useful PK/PD and doseaccuracy. For example, it has been found that placement of the needleoutlet within the skin significantly affects PK/PD parameters. Theoutlet of a conventional or standard gauge needle with a bevel has arelatively large exposed height (the vertical rise of the outlet).Although the needle tip may be placed at the desired depth within theintradermal space, the large exposed height of the needle outlet causesthe delivered substance to be deposited at a much shallower depth nearerto the skin surface. As a result, the substance tends to effuse out ofthe skin due to backpressure exerted by the skin itself and to pressurebuilt up from accumulating fluid from the injection or infusion. Thatis, at a greater depth a needle outlet with a greater exposed heightwill still seal efficiently where as an outlet with the same exposedheight will not seal efficiently when placed in a shallower depth withinthe intradermal space. Typically, the exposed height of the needleoutlet will be from 0 to about 1 mm. A needle outlet with an exposedheight of 0 mm has no bevel and is at the tip of the needle. In thiscase, the depth of the outlet is the same as the depth of penetration ofthe needle. A needle outlet that is either formed by a bevel or by anopening through the side of the needle has a measurable exposed height.It is understood that a single needle may have more than one opening oroutlets suitable for delivery of substances to the dermal space.

It has also been found that by controlling the pressure of injection orinfusion may avoid the high backpressure exerted during IDadministration. By placing a constant pressure directly on the liquidinterface a more constant delivery rate can be achieved, which mayoptimize absorption and obtain the improved pharmacokinetics. Deliveryrate and volume can also be controlled to prevent the formation ofwheals at the site of delivery and to prevent backpressure from pushingthe dermal-access means out of the skin. The appropriate delivery ratesand volumes to obtain these effects for a selected substance may bedetermined experimentally using only ordinary skill. Increased spacingbetween multiple needles allows broader fluid distrubtion and increasedrates of delivery or larger fluid volumes. In addition, it has beenfound that ID infusion or injection often produces higher initial plasmalevels of drug than conventional SC administration, particularly fordrugs that are susceptible to in vivo degradation or clearance or forcompounds that have an affinity to the SC adipose tissue or formacromolecules that diffuse slowly through the SC matrix. This may, inmany cases, allow for smaller doses of the substance to be administeredvia the ID route.

The administration methods useful for carrying out the invention includeboth bolus and infusion delivery of drugs and other substances to humansor animals subjects. A bolus dose is a single dose delivered in a singlevolume unit over a relatively brief period of time, typically less thanabout 10 minutes. Infusion administration comprises administering afluid at a selected rate that may be constant or variable, over arelatively more extended time period, typically greater than about 10minutes. To deliver a substance the dermal-access means is placedadjacent to the skin of a subject providing directly targeted accesswithin the intradermal space and the substance or substances aredelivered or administered into the intradermal space where they can actlocally or be absorbed by the bloodstream and be distributedsystematically. The dermal-access means may be connected to a reservoircontaining the substance or substances to be delivered. The form of thesubstance or substances to be delivered or administered includesolutions thereof in pharmaceutically acceptable diluents or solvents,emulsions, suspensions, gels, particulates such as micro- andnanoparticles either suspended or dispersed, as well as in-situ formingvehicles of the same. Delivery from the reservoir into the intradermalspace may occur either passively, without application of the externalpressure or other driving means to the substance or substances to bedelivered, and/or actively, with the application of pressure or otherdriving means. Examples of preferred pressure generating means includepumps, syringes, elastomer membranes, gas pressure, piezoelectric,electromotive, elecrtomagnetic pumping, or Belleville springs or washersor combinations thereof. If desired, the rate of delivery of thesubstance may be variably controlled by the pressure-generating means.As a result, the substance enters the intradermal space and is absorbedin an amount and at a rate sufficient to produce a clinicallyefficacious result.

As used herein, the term “clinically efficacious result” is meant aclinically useful biological response including both diagnostically andtherapeutically useful responses, resulting from administration of asubstance or substances. For example, diagnostic testing or preventionor treatment of a disease or condition is a clinically efficaciousresult. Such clinically efficacious results include diagnositic resultssuch as the measurement of glomerular filtration pressure followinginjection of inulin, the diagnosis of adrenocortical function inchildren following injection of ACTH, the causing of the gallbladder tocontract and evacuate bile upon injection of cholecystokinin and thelike as well as therapeutic results, such as clinically adequate controlof blood sugar levels upon injection of insulin, clinically adequatemanagement of hormone deficiency following hormone injection such asparathyroid hormone or growth hormone, clinically adequate treatment oftoxicity upon injection of an antitoxin and the like.

Substances that can be delivered intradermally in accordance with thepresent invention are intended to include pharmaceutically orbiologically active substances including include diagnostic agents,drugs, and other substances which provide therapeutic or health benefitssuch as for example nutraceuticals. Diagnostic substances useful withthe present invention include macromolecular substances such as, forexample, inulin, ACTH (e.g. corticotropin injection), luteinizinghormone-releasing hormone (eg., Gonadorelin Hydrochloride), growthhormone-releasing hormone (e.g. Sermorelin Acetate), cholecystokinin(Sincalide), parathyroid hormone and fragments thereof (e.g.Teriparatide Acetate), thyroid releasing hormone and analogs thereof(e.g. protirelin), secretin and the like.

Therapeutic substances which can be used with the present inventioninclude Alpha-1 anti-trypsin, Anti-Angiogenesis agents, Antisense,butorphanol, Calcitonin and analogs, Ceredase, COX-II inhibitors,dermatological agents, dihydroergotamine, Dopamine agonists andantagonists, Enkephalins and other opioid peptides, Epidermal growthfactors, Erythropoietin and analogs, Follicle stimulating hormone,G-CSF, Glucagon, GM-CSF, granisetron, Growth hormone and analogs(including growth hormone releasing hormone), Growth hormoneantagonists, Hirudin and Hirudin analogs such as Hirulog, IgEsuppressors, Insulin, insulinotropin and analogs, Insulin-like growthfactors, Interferons, Interleukins, Luteinizing hormone, Luteinizinghormone releasing hormone and analogs, Heparins, Low molecular weightheparins and other natural, modified, or syntheic glycoaminoglycans,M-CSF, metoclopramide, Midazolam, Monoclonal antibodies, Peglyatedantibodies, Pegylated proteins or any proteins modified with hydrophilicor hydrophobic polymers or additional functional groups, Fusionproteins, Single chain antibody fragments or the same with anycombination of attached proteins, macromolecules, or additionalfunctional groups thereof, Narcotic analgesics, nicotine, Non-steroidanti-inflammatory agents, Oligosaccharides, ondansetron, Parathyroidhormone and analogs, Parathyroid hormone antagonists, Prostaglandinantagonists, Prostaglandins, Recombinant soluble receptors, scopolamine,Serotonin agonists and antagonists, Sildenafil, Terbutaline,Thrombolytics, Tissue plasminogen activators, TNF-, and TNF-antagonist,the vaccines, with or without carriers/adjuvants, includingprophylactics and therapeutic antigens (including but not limited tosubunit protein, peptide and polysaccharide, polysaccharide conjugates,toxoids, genetic based vaccines, live attenuated, reassortant,inactivated, whole cells, viral and bacterial vectors) in connectionwith, addiction, arthritis, cholera, cocaine addiction, diphtheria,tetanus, HIB, Lyme disease, meningococcus, measles, mumps, rubella,varicella, yellow fever, Respiratory syncytial virus, tick bornejapanese encephalitis, pneumococcus, streptococcus, typhoid, influenza,hepatitis, including hepatitis A, B, C and E, otitis media, rabies,polio, HIV, parainfluenza, rotavirus, Epstein Barr Virus, CMV,chlamydia, non-typeable haemophilus, moraxella catarrhalis, humanpapilloma virus, tuberculosis including BCG, gonorrhoea, asthma,atheroschlerosis malaria, E-coli, Alzheimer's Disease, H. Pylori,salmonella, diabetes, cancer, herpes simplex, human papilloma and thelike other substances including all of the major therapeutics such asagents for the common cold, Anti-addiction, anti-allergy, anti-emetics,anti-obesity, antiosteoporeteic, anti-infectives, analgesics,anesthetics, anorexics, antiarthritics, antiasthmatic agents,anticonvulsants, anti-depressants, antidiabetic agents, antihistamines,anti-inflammatory agents, antimigraine preparations, antimotion sicknesspreparations, antinauseants, antineoplastics, antiparkinsonism drugs,antipruritics, antipsychotics, antipyretics, anticholinergics,benzodiazepine antagonists, vasodilators, including general, coronary,peripheral and cerebral, bone stimulating agents, central nervous systemstimulants, hormones, hypnotics, immunosuppressives, muscle relaxants,parasympatholytics, parasympathomimetrics, prostaglandins, proteins,peptides, polypeptides and other macromolecules, psychostimulants,sedatives, and sexual hypofunction and tranquilizers.

Pharmacokinetic analysis of insulin infusion data was carried out asfollows. Stepwise nonlinear least-squares regression was used to analyzethe insulin concentration-time data from each individual animal.Initially, an empirical biexponential equation was fit to the insulinconcentration-time data for the negative control condition. Thisanalysis assumed first-order release of residual insulin, and recoveredparameters for the first-order rate constant for release, the residualinsulin concentration at the release site, a lag time for release, and afirst-order rate constant for elimination of insulin from the systemiccirculation. The parameters recovered in this phase of the analysis areof no intrinsic importance, but merely account for the fraction ofcirculating insulin derived from endogenous sources.

The second step of the analysis involved fitting an explicitcompartmental model to the insulin concentration-time data during andafter subcutaneous or intradermal infusion. The scheme upon which themathematical model was based is shown in the upper part of FIG. 1.[PK/PD model FIG]. Infusion of insulin proceeded from t=0 to t=240 min;after a lag time (t_(lag,2)), absorption from the infusion site wasmediated by a first-order process governed by the absorption rateconstant k_(a). Insulin absorbed into the systemic circulationdistributed into an apparent volume V contaminated by an unknownfractional bioavailability F, and was eliminated according to afirst-order rate constant K. The fitting routine recovered estimates oft_(lag,2), k_(a), V/F, and K; parameters associated with the dispositionof endogenous insulin (C_(R), t_(lag,1), k_(R)), which were recovered inthe first step of the analysis, were treated as constants.

Parameter estimates are reported as mean±SD. The significance ofdifferences in specific parameters between the two different modes ofinsulin administration (subcutaneous versus intradermal infusion) wasassessed with the paired Student's t-test.

Pharmacodynamic analysis of insulin infusion data was calculated asfollows. Plasma concentrations of glucose were used as a surrogate forthe pharmacological effect of insulin. The change in response variable R(plasma glucose concentration) with respect to time t was modeled as

$\frac{\mathbb{d}R}{\mathbb{d}t} = {k_{in} - {E \cdot k_{out}}}$

where k_(in) is the zero-order infusion of glucose, o_(ut) is thefirst-order rate constant mediating glucose elimination, and E is theeffect of insulin according to the sigmoid Hill relationship

$E = \frac{E_{\max} \cdot C^{\gamma}}{{EC}_{50}^{\gamma} + C^{\gamma}}$

in which M_(ax) is the maximal stimulation of o_(ut) by insulin, EC₅₀ isthe insulin concentration at which stimulation of o_(ut) is halfmaximal, C is the concentration of insulin, and γ is the Hillcoefficient of the relationship. Initial modeling efforts utilized theplasma concentration of insulin as the mediator of pharmacologicalresponse. However, this approach did not capture the delay in responseof plasma glucose to increasing concentrations of plasma insulin.Therefore, an effect-compartment modeling approach was finally adoptedin which the effect of insulin was mediated from a hypothetical effectcompartment peripheral to the systemic pharmacokinetic compartment

The pharmacodynamic analysis was conducted in two steps. In the firststep of the analysis, initial estimates of the pharmacokineticparameters associated with the disposition of glucose (o_(ut) and thevolume of distribution of glucose, V_(glucose)) were determined from theglucose concentration-time data in the negative control condition. Thefull integrated pharmacokinetic-pharmacodynamic model then was fitsimultaneously to the glucose concentration-time data from the negativecontrol condition and each insulin delivery condition for each animal(i.e., two sets of pharmacodynamic parameters were obtained for eachanimal: one from the simultaneous analysis of the subcutaneous insulininfusion/negative control data, and one from the simultaneous analysisof the intradermal insulin infusion/negative control data). In allpharmacodynamic analyses, the parameters governing insulin dispositionobtained during pharmacokinetic analysis of insulin concentration-timedata from each animal were held constant.

All other pharmacokinetic analyses were calculated usingnon-compartmental methods using similar sofware programs and techniquesknown in the art.

Having described the invention in general, the following specific butnot limiting examples and reference to the accompanying Figures setforth various examples for practicing the dermal accessing, directtargeting drug administration method and examples of dermal administereddrug substances providing improved PK and PD effects.

A representative example of dermal-access microdevice comprising asingle needle were prepared from 34 gauge steel stock (MicroGroup, Inc.,Medway, Mass.) and a single 28° bevel was ground using an 800 gritcarborundum grinding wheel. Needles were cleaned by sequentialsonication in acetone and distilled water, and flow-checked withdistilled water. Microneedles were secured into small gauge cathetertubing (Maersk Medical) using UV-cured epoxy resin. Needle length wasset using a mechanical indexing plate, with the hub of the cathetertubing acting as a depth-limiting control and was confirmed by opticalmicroscopy. For experiments using needles of various lengths, theexposed needle lengths were adjusted to 0.5, 0.8, 1, 2 or 3 mm using theindexing plate. Connection to the fluid metering device, either pump orsyringe, was via an integral Luer adapter at the catheter inlet. Duringinjection, needles were inserted perpendicular to the skin surface, andwere either held in place by gentle hand pressure for bolus delivery orheld upright by medical adhesive tape for longer infusions. Devices werechecked for function and fluid flow both immediately prior to and postinjection. This Luer Lok single needle catheter design is hereafterdesignated SS1_(—)34.

Yet another dermal-access array microdevices was prepared consisting of1″ diameter disks machined from acrylic polymer, with a low volume fluidpath branching to each individual needle from a central inlet. Fluidinput was via a low volume catheter line connected to a Hamiltonmicrosyringe, and delivery rate was controlled via a syringe pump.Needles were arranged in the disk with a circular pattern of 15 mmdiameter. Three-needle and six-needle arrays were constructed, with 12and 7 mm needle-to-needle spacing, respectively. All array designs usedsingle-bevel, 34 G stainless steel microneedles of 1 mm length. The3-needle 12 mm spacing catheter-design is hereafter designatedSS3_(—)34B, 6-needle 7 mm spacing catheter-design is hereafterdesignated SS6_(—)34A.

Yet another dermal-access array microdevices was prepared consisting of11 mm diameter disks machined from acrylic polymer, with a low volumefluid path branching to each individual needle from a central inlet.Fluid input was via a low volume catheter line connected to a Hamiltonmicrosyringe, and delivery rate was controlled via a syringe pump.Needles were arranged in the disk with a circular pattern of about 5 mmdiameter. Three-needle arrays of about 4 mm spacing connected to acatheter as described above. These designs are hereafter designatedSS3S_(—)34_(—)1, SS3C_(—)34_(—)2, and SS3S_(—)34_(—)3 for 1 mm, 2 mm,and 3 mm needle lengths respectively.

Yet another dermal-access ID infusion device was constructed using astainless steel 30 gauge needle bent at near the tip at a 90-degreeangle such that the available length for skin penetration was 1-2 mm.The needle outlet (the tip of the needle) was at a depth of 1.7-2.0 mmin the skin when the needle was inserted and the total exposed height ofthe needle outlet 1.0-1.2 mm This design is hereafter designatedSSB1_(—)30.

EXAMPLE I

Slow-infusion ID insulin delivery was demonstrated in swine using ahollow, silicon-based single-lumen microneedle (2 mm total length and200×100 μm OD, corresponding to about 33 gauge) with an outlet 1.0 μmfrom the tip (100 μm exposed height), was fabricated using processesknown in the art (U.S. Pat. No. 5,928,207) and mated to a microborecatheter (Disetronic). The distal end of the microneedle was placed intothe plastic catheter and cemented in place with epoxy resin to form adepth-limiting hub. The needle outlet was positioned approximately 1 mmbeyond the epoxy hub, thus limiting penetration of the needle outletinto the skin to approximately 1 mm., which corresponds to the depth ofthe intradermal space in swine. The catheter was attached to a MiniMed507 insulin pump for control of fluid delivery. The distal end of themicroneedle was placed into the plastic catheter and cemented in placewith epoxy resin to form a depth-limiting hub. The needle outlet waspositioned approximately 1 mm beyond the epoxy hub, thus limitingpenetration of the needle outlet into the skin to approximately 1 mm.,which corresponds to the depth of the intradermal space in swine. Thepatency of the fluid flow path was confirmed by visual observation, andno obstructions were observed at pressures generated by a standard 1-ccsyringe. The catheter was connected to an external insulin infusion pump(MiniMed 507) via the integral Luer connection at the catheter outlet.The pump was filled with Humalog™ (Lispro) insulin (Eli Lilly,Indianapolis, Ind.) and the catheter and microneedle were primed withinsulin according to the manufacturer's instructions. Sandostatin®(Sandoz, East Hanover, N.J.) solution was administered via IV infusionto anesthetized swine to suppress basal pancreatic function and insulinsecretion. After a suitable induction period and baseline sampling, theprimed microneedle was inserted perpendicular to the skin surface in theflank of the animal up to the hub stop. Insulin infusion at a rate of 2U/hr was used and maintained for 4 hr. Blood samples were periodicallywithdrawn and analyzed for serum insulin concentration and blood glucosevalues. Baseline insulin levels before infusion were at the backgrounddetection level of the assay. After initiation of the infusion, seruminsulin levels showed an increase that was commensurate with theprogrammed infusion rates. Blood glucose levels also showed acorresponding drop relative to negative controls (NC) without insulininfusion and this drop was improved relative to conventional SCinfusion. In this experiment, the microneedle was demonstrated toadequately breach the skin barrier and deliver a drug in vivo atpharmaceutically relevant rates. The ID infusion of insulin wasdemonstrated to be a pharmacokinetically acceptable administrationroute, and the pharmacodynamic response of blood glucose reduction wasalso demonstrated. Calculated PK parameters for ID infusion indicatethat insulin is absorbed much faster than via than SC administration.Absorption from the ID space begins almost immediately: the lag timeprior to absorption (t_(lag)) was 0.88 vs. 13.6 min for ID and SCrespectively. Also the rate of uptake from the administration site isincreased by approximately 3-fold, k_(a)=0.0666 vs. 0.0225 min⁻¹ for IDand SC respectively. The bioavailability of insulin delivered by IDadministration is increased approximately 1.3 fold greater than SCadministration.

EXAMPLE II

Bolus delivery of Lilly Lispro fast acting insulin was performed usingID and SC bolus administration. The ID injection microdevice was dermalaccess array design SS3_(—)34. 10 international insulin units (U)corresponding to 100 uL volume respectively, were administered todiabetic Yucatan Mini swine. Test animals had been previously beenrendered diabetic by chemical ablation of pancreatic islet cells, andwere no longer able to secrete insulin. Test animals received theirinsulin injection either via the microneedle array or via a standard 30G X ½ in. needle inserted laterally into the SC tissue space.Circulating serum insulin levels were detected using a commercialchemiluminescent assay kit (Immulite, Los Angeles, Calif.) and bloodglucose values were determined using blood glucose strips. ID injectionswere accomplished via hand pressure using an analytical microsyringe andwere administered over approximately 60 sec. By comparison, SC dosingrequired only 2-3 sec. Referring to FIG. 1, it is shown that seruminsulin levels after bolus administration demonstrate more rapid uptakeand distribution of the injected insulin when administered via the IDroute. The time to maximum concentration (T_(max)) is shorter and themaximum concentration obtained (C_(max)) is higher for ID vs. SCadministration. In addition, FIG. 2 also demonstrates thepharmacodynamic biological response to the administered insulin, asmeasured by the decrease in blood glucose (BG), showed faster andgreater changes in BG since more insulin was available early after IDadministration.

EXAMPLE III

Lilly Lispro is regarded as fact acting insulin, and has a slightlyaltered protein structure relative to native human insulin. Hoechstregular insulin, maintains the native human insulin protein structurethat is chemically similar, but has slower uptake than Lispro whenadministered by the traditional SC route. Both insulin types wereadministered in bolus via the ID route to determine if any differencesin uptake would be discernable by this route. 5 U of either insulin typewere administered to the ID space using dermal access microdevice designSS3_(—)34. The insulin concentration verses time data shown in FIG. 3.When administered by the ID route the PK profiles for regular andfast-acting insulin were essentially identical, and both insulin typesexhibited faster uptake than Lispro given by the traditional SC route.This is evidence that the uptake mechanism for ID administration is lessaffected by minor biochemical changes in the administered substance, andthat ID delivery provides an advantageous PK uptake profile for regularinsulin that is superior to SC administered fast-acting insulin.

EXAMPLE IV

Bolus delivery of Lilly Lispro fast-acting insulin via microneedlearrays having needles of various lengths was conducted to demonstratethat the precise deposition of drug into the dermal space is necessaryto obtain the PK advantages and distinctions relative to SC. Thus, 5 Uof Lilly Lispro fast-acting insulin was administered using dermal accessdesign SS3_(—)34. Additional microdevices of the same needle arrayconfiguration were fabricated whereby exposed needle lengths of themicrodevice array were lengthened to include arrays with needles lengthsof 2 and 3 mm. The average total dermal thickness in Yucatan Mini swineranges from 1.5-2.5 mm. Therefore insulin deposition is expected to beinto the dermis, approximately at the dermal/SC interface, and below thedermis and within the SC for 1 mm, 2 mm, and 3 mm length needlesrespectively. Bolus insulin administration was as described in EXAMPLEII. Average insulin concentrations verses time are shown in FIG. 4. Thedata clearly shows as microneedle length is increased, the resulting PKprofile begins to more closely resemble SC administration. This datademonstrates the benefits of directly targeting the dermal space, suchbenefits include rapid uptake and distribution, and high initialconcentrations. Since the data are averages of multiple examples, theydo not show the increased inter-individual variability in PK profilesfrom longer 2 and 3 mm microneedles. This data demonstrates that sinceskin thickness may vary both between individuals and even within asingle individual, shorter needle lengths that accurately target thedermal space are more reproducible in their PK profile since they aredepositing the drug more consistently in the same tissue compartment.This data demonstrates longer microneedles that deposit or administersubstances deeper into the dermal space, or partially or wholly into theSC space, mitigate or eliminate the PK advantages in comparison toshallow, directly targeted administrations to the highly vascularizeddermal region.

EXAMPLE V

Bolus delivery of Lantus long-acting insulin was delivered via the IDroute. Lantus is an insulin solution that forms microprecipitates at theadministration site upon injection. These microparticulates undergo slowdissolution within the body to provide (according to the manufacturer'sliterature) a more stable low level of circulating insulin than othercurrent long-acting insulin such as crystalline zinc precipitates (e.g.Lente, NPH). Lantus insulin (10 U dose, 100 uL) was administered todiabetic Yucatan Mini pigs using the dermal access design SS3_(—)34 andby the standard SC method as previously described. Referring to FIG. 5,when administered via the ID route, similar PK profiles were obtainedrelative to SC. Minor distinctions include a slightly higher “burst”immediately after the ID insulin delivery. This demonstrates that theuptake of even very high molecular weight compounds or small particlesis achievable via ID administration. More importantly this supports thefact that the biological clearance mechanism in the body is notappreciably changed by the administration route, nor is the way in whichthat the drug substance is utilized. This is extremely important fordrugs compounds that have a long circulating half-life (examples wouldbe large soluble receptor compounds or other antibodies for cancertreatment, or chemically modified species such as PEGylated drugs).

EXAMPLE VI

Bolus ID delivery of human granulocyte colony stimulating factor (GCSF)(Neupogen) was administered via dermal access microdevice designsSS3_(—)34B (array) or SS1_(—)34 (single needle) to Yucatan minipigs.Delivery rate was controlled via a Harvard syringe pump and wasadministered over a 1-2.5 min period. FIG. 6 shows the PK availabilityof GCSF in blood plasma as detected by an ELISA immunoassay specific forGCSF. Administration via IV and SC delivery was performed as controls.Referring to FIG. 6 bolus ID delivery of GCSF shows the more rapiduptake associated with ID delivery. C_(max) is achieved at approximately30-90 minutes vs. 120 min for SC. Also the bioavailability isdramatically increased by an approximate factor of 2 as evidenced by themuch higher area under the curve (AUC). Circulating levels of GCSF aredetectable for an extended period, indicting that ID delivery does notalter the intrinsic biological clearance mechanism or rate for the drug.These data also show that device design has minimal effect on the rapiduptake of drug from the ID space. The data referred to in FIG. 7 alsoshows the degree and time course of white blood cell expansion as aresult of GCSF administration with respect to a negative control (noGCSF administered). White blood cell (WBC) counts were determined bystandard cytometric clinical veterinary methods ID delivery exhibits thesame clinically significant biological outcomes. Although all deliverymeans give approximately equal PD outcomes, this data suggests IDdelivery could enable use half the dose to achieve essentially the samephysiological result in comparison to SC, due to approximately 2-foldbioavailability increase.

EXAMPLE VII

An ID administration experiment was conducted using a peptide drugentity: human parathyroid hormone 1-34 (PTH). PTH was infused for a 4 hperiod, followed by a 2 h clearance. Control SC infusion was through astandard 31-gauge needle inserted into the SC space lateral to the skinusing a “pinch-up” technique. ID infusion was through dermal accessmicrodevice design SSB1_(—)30 (a stainless steel 30-gauge needle bent atthe tip at a 90° angle such that the available length for skinpenetration was 1-2 mm). The needle outlet (the tip of the needle) wasat a depth of 1.7-2.0 mm in the skin when the needle was inserted. A0.64 mg/mL PTH solution was infused at a rate of 75 μL/hr. Flow rate wascontrolled via a Harvard syringe pump. Weight normalized PTH plasmalevels are shown in Figure XX. {The weight normalized delivery profilesshow a larger area under the curve (AUC) indicating higherbioavailability, higher peak values at earlier sampling timepoints (e.g.15 and 30 min) indicating more rapid onset from ID delivery, and rapiddecrease following termination of infusion (also indicative of rapiduptake without a depot effect).}

The above examples and results demonstrate the inventive delivery methodusing multi-point array ID administration and single needle IDadministration results in more rapid uptake with higher C_(max) than SCinjection. ID uptake and distribution is ostensibly unaffected by devicegeometry parameters, using needle lengths of about 0.5 to about 1.7 mm,needle number and needle spacing. No concentration limit for biologicalabsorption was found and PK profiles were dictated principally by theconcentration-based delivery rate. The primary limitations of IDadministration are the total volume and volumetric infusion-rate limitsfor leak-free instillation of exogenous substances into a dense tissuecompartment. Since absorption of drugs from the ID space appears to beinsensitive to both device design and volumetric infusion rate, numerousformulation/device combinations can be used to overcome this limitationsand provide the required or desired therapeutic profiles. For example,volume limited dosing regimens can be circumvented either by using moreconcentrated formulations or increasing the total number of instillationsites. In addition, effective PK control is obtained by manipulatinginfusion or administration rate of substances.

In general, ID delivery as taught by the methods described hereto viadermal access microneedle devices provides a readily accessible andreproducible parenteral delivery route, with high bioavailability, aswell as the ability to modulate plasma profiles by adjusting the deviceinfusion parameters, since uptake is not rate-limited by biologicaluptake parameters.

In the previously described examples, the methods practiced by theinvention demonstrate the ability to deliver a drug in vivo with greatlyimproved pharmaceutically relevant rates. This data indicates animproved pharmacological result for ID administration as taught by themethods described of other drugs in humans would be expected accordingto the methods of the invention.

All references cited in this specification are hereby incorporated byreference. The discussion of the references herein is intended merely tosummarize the assertions made by their authors and no admission is madethat any reference constitutes prior art relevant to patentability.Applicants reserve the right to challenge the accuracy and pertinency ofthe cited references.

What is claimed is:
 1. A method for administration of a drug to a human subject, comprising delivering the drug through the lumen of a hollow needle into an intradermal compartment of the human subject's skin, which method comprises (a) inserting the needle into the subject's skin so that the needle penetrates the intradermal compartment, and the needle's outlet depth and exposed height of the outlet are located within the intradermal compartment, wherein the outlet has an exposed height of 0 to about 1 mm; and (b) delivering the drug through the lumen of the needle with the application of pressure in an amount effective to control the rate of delivery of the drug, so that the drug is delivered through the lumen of the needle into the intradermal compartment and distributed systemically exhibiting any one of the following improved pharmacokinetic parameters as compared to subcutaneous delivery: (i) a higher maximum plasma concentration and a higher bioavailability; (ii) a higher maximum plasma concentration and a decreased time to elicit a minimally detectable blood or plasma concentration; (iii) a higher bioavailability and a decreased time to elicit a minimally detectable blood or plasma concentration; (iv) a higher bioavailability and decreased decreased time to maximal plasma concentration; or (v) a decreased time to elicit a minimally detectable blood or plasma concentration and decreased time to maximal plasma concentration.
 2. The method of claim 1, wherein the needle is selected from the group consisting of microneedles, catheter needles, and injection needles.
 3. The method of claim 1, wherein a single needle is inserted.
 4. The method of claim 1, wherein multiple needles are inserted.
 5. The method of claim 1, wherein the substance is a liquid delivered by pressure directly on the liquid.
 6. The method of claim 1, wherein the needle has a length from about 0.5 to about 1.7 mm.
 7. The method of claim 1, wherein the needle's outlet depth is between about 0.3 mm a to 2 mm when the needle is inserted.
 8. The method of claim 1, wherein the outlet has an exposed height of 0 mm.
 9. The method of claim 1, wherein the delivery rate or volume is controlled by spacing of multiple needles.
 10. The method of claim 1, wherein the improved pharmacokinetic parameters are a higher maximum plasma concentration and a higher bioavailability.
 11. The method of claim 1, wherein the improved pharmacokinetic parameters are a higher maximum plasma concentration and a decreased time to elicit a minimally detectable blood or plasma concentration.
 12. The method of claim 1, wherein the improved pharmacokinetic parameters are a higher bioavailability and a decreased time to elicit a minimally detectable blood or plasma concentration.
 13. The method of claim 1, wherein the improved pharmacokinetic parameters are a higher bioavailability and decreased time to maximal plasma concentration.
 14. The method of claim 1, wherein the improved pharmacokinetic parameters are a decreased time to elicit a minimally detectable blood or plasma concentration and decreased time to maximal plasma concentration. 